Electric resistance unit.



E. N. LIGHTFO0T. ELECTRIC RESISTANCE UNIT. APPLIOATION FILED DBO. 14, 1911.

Patented 1186.10, 1912.

2 SHEETS-SHEET 1.

E. N. LIGHTPOOT.

ELECTRIC RESISTANCE um.

APPLICATION FILED DEO. 14. 1911.

1,046,81 6. Patented Dec.10,1912. l 2 SHEETS-SHEET 2.

QQ /Q /9 am zum UNITED STATES PATENT carica.

ELECTRIC RESISTANCE UNIT.

Application led December 14, 1911.

To all whom t may concern:

Be it known that I, EDWIN N. LrGH'rFoo'r,

a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented new and j useful Improvements in Electric Resistance 4 Units, of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part of this specification.

My invention relates to electric resistance units. These units are particularly adapted to be employed in electric heating appliances.4

In practice it is difficult to rmly support a resistance of small cross sect-ion and at the same time provide for maximum radiation and etticiency within a given space. Resist-ance units have been made wherein VVthe resistance is convoluted and is supported by a rod which passes through its convolutions. In order to provide for rapid radiation of the heat and to obtain great eiiiciency, the resistance is so formed that it merely engages the rod at certain points, other points of the resistance being spaced from the rod.

The object of the present invention is to so form the resistance that it will -be firmly su ported by the rod without impairing its e ciency. To attain this end, a convoluted resistance in which each convolution is 'triangular in form, is supported by an insulating rod which passes through -the convolutions. lution engage the supporting rod substantially tangentially so that each side is iirmly held upon the supporting rod by its two adjacent sides. The convolutions are of such form and size that merely a small portion thereof engages the rod. Each convolution is thus firmly maintained in position and at the same time the resistance is allowed to rapidly radiate the heat and obtain maximum eiiiciency. The resistance may be made of any suitable material and is preferably in the form of a wire, ribbon, or strip. The structure which the invention provides makes it possible to readily employ a resistance of minute cross Section.

In practice the invention may assume various forms. Several units -embodying the invention are illustrated in the accompanying drawings. They have been selected merel for the purpose of illustration and there ore itwill be understood that other Specification of Letters Patent.

The three sides of each convoy Patented Dec. 10, 1912. serial No. 655,788.

'structures which attain the purpose in View are within the scope of the invention.

The views in the drawings are as fol- .lows:-

Figure l shows a side elevationof one form of unit; Fig. 2 shows an enlarged deftail View of one form of terminal connec- `tion for the unit; Fig. 3 shows a modified form of terminal connection; Fig. 4 shows a Qside elevation of another form of resistance `lunit. Fig. 5 Shows a detail view of a vpor- @tion` of the same. Fig. 6 shows a unit Qmounted in a support. Fig. 7 shows a unit `mounted in a modied form of support. SFig. 8 shows a unit mounted in another modified form of support. Fig. 9 shows a jpe'rspective View of one of the supporting trods shown in Fig. 8. Fig. 10 shows one means of connecting adjacent resistance units.

In the constructions shown for purposes of illustration I have illustrated a plurality of forms of my improved resistance unit, including a. slotted, bent, reexed or otherwise formed strip of resistance material 1 having the ends ot' its adjacent convolutions spirally arranged and extending in different 4.angular directions; an insulating support 2 extending through said convolutions and `acting as ameans for insulating and spacing the convolutions of the same, and at the same time as a means for supporting the same in the desired relation.

In Figs. 1 to 3 inclusive I have shown an 'electric resistance unit formed of slotted resistance ribbon made of any desired resistance material. This resistance ribbon has Vits adjacent convolutions bent in opposite directions so that a substantially triangular shaped section of resistance material is formed in which parts of the convolutions of resistance material form the sides ot' the triangle. For instance, taking the convolutions 3 and 4 shown in Fig. l, when the resistance material is in the form ot' the slotted strip the convolution 4 lies above the convolution 8, as shown .in Fig. 2. lVhen it is desired to shape the unit as shown in Fig. l, the convolution 4 is forced over to the right, leaving the convolution 3 at the lett. The upper half of the convolution 4 is then brought again to the right and the adjacent halves of the convolutions are successively moved to the'right and left in this manner to provide a resistance section of the shape erred form, 1 use quartz-glass,

^ may use ordinary glass the insulating support.

shown in Fig. 1, wherein the unslotted ends of the resistance material extend in a plurality of different radial positions. Thus it is seen that in this form of unit the ends of'. the convolutions are arranged in three rows, and that a central opening is provided in which the insulating support may be inserted.

While in the ldrawings the projecting ends or points of the convolutions are shown in straight rows or in alinement it should, of course, be understood that this regularity is not necessary as the projecting ends orr points of adjacent convolutions might be arranged at relatively different angles if desired.

The insulating support 2 maybe formed of any suitable insulating material of a type which is adapted to serve not only as a support for the resistance material, but also as a' 'means for insulating the same. ln a premagnesite or the like, in making up this support, since such materials are capable of standing up under very high temperatures. ln constructions designed to operate at lower temperatures l may use an insulating material having a lower melting point. lt desired, .l as the material for ln the use of such a material l t'md that l am able to provide a support of great stability, since when the insulating material is brought to a high temperature it is melted slightly so that the resistance material embeds itself more or less in the` same, forming a substantially unitary device. l

In Fig. 2 l have illustrated an end connection or terminal connection which may be used with a resistance material of the type shown in Fig. l. As shown in this construction, the erd 5 of the resistance material may be left unslotted and may be bent over as at 6 along a substantially 'diagonal line to form two-aps. A perforation 7 may be providednear the treei end of the unslotted portion, and a plurality of registering perforations 8 may be provided in the bent-over portions. When it is desired to provide a terminal connection for'the unit of such a construction, all that it is necessary to do is to Jfold together the ends in which the perforations 'Z' and 8 are made, so that they lie in substantially parallel planes, as shown in Fig. l, and then connect them by any suitable binding screw or other suitable device 9, to'which a line conductor may be attached. i o

in Fig. 3 l have illustrated a further modified form oi terminal connection. as shown in this construction, instead ot leaving the end unslotted, as shown in Fig. 2, 1 may clip the end of the unit adjacent to the end of the slotted portion and bend one or more turns ot the slotted portion around.

-conducting rods 14 and 15 as at 17, by

the insulating support 2, so that it may be readily inclosed in a suitable conducting clip 10 having perforations in its flaps 11 arranged to receive a suitable binding screw 12. 1t is to be noted that in this construction, instead of having-the unslotted end of the resistance material form the clip for.

holding the binding screw, l: provide a separate holding clip for the binding screw.

In a preferred form when l use ka retlexed resistance material, ll slightly bend out or round the portion of the resistance material between the ends of the convolutions as at 13, in order to provide a better contact with the support. As shown in this construction the terminal connections may be, if desired, the same as those shown in Fig. 3, the ends of the reflexed material being inclosed between the clips 10. y

In Figs. 4 and 5 1 have illustrated a turther moditied form of resistance material which l may use, it desired. rlhis resistance material is made up from a resistance material in the form of a tape which may be wound on a mandrel in the form of a helix, and then iattened so that it assumes a substantially triangular form,l as shown in these figures. if desired, the terminal connections for the same may be substantially the same as those ll have shown in Fig.3, although in this instance since there are no slotted convolutions the last convolution of the helix may be bent over substantially at 4 right angles and brought up along the tube before it is brought around the tube, as shown in that gure.

lnFig. 6 l have illustrated a preferred form of construction wherein l employ two or more resistance units. supports 2 carrying these resistance units are preferably made up in the form of tubes loosely fitted upon a plurality of metal rods 14 and 15. 1n the construction shown l have illustrated two rods 14 and two rods 15, the rods'14 and 15 being xed in a suitable rame 16 preferably formed of insulat ing material. ln the construction shown the rods of each set 14 and 15 do not extend en tirely through the two insulating tubes 2, but enter the tubes from each end and are shorter than the tubes, so that there is a space between the inner ends of the rods which, upon the expansion or contraction `oit the same, permits vt iem to move freely to adthemselves upon the changes in temperature.

The insulating itl() ploy two or more resistance units 'I prefer-` ably so arrange the electrical connections for the units that the rods 14 and 15 may serve as the terminals for the `device. ln this construction the ends of the resistance material are preferably attached to the any suitable means, so that they engage with the metal rods in such a manner as to uic-,lic

a good electrical. contact.` If desired, they may be spot-welded thereto. The outer ends of one set of rods are preferably elect-rically connected as for instance by'a conductor 18, which may extend between suitable binding screws 19 carried upon the ends of the rod in any suitable manner as by threading, if desired. The opposite ends of the other set of rods may be provided with similar binding posts 19 in order that they may be connected to the line conductors.

In Fig. 7 I have illustrated diagrammatically a preferred manner of mounting my resistance unit in a support. The insulating support 2, as heretofore described, is preferably made hollow and tubular in form so that it may receive a rod 22. This rod 22 in this construction preferably extends entirely through the tube 2, upon which it is loosely fitted. 'In a preferred form, one end of this rod is fired, as by embedding if desired, in an insulating base 21, while the other end is free to move in its support, as for instance in a second insulating base 20. The two base members 20 and 21 may obviously be in the form of a frame, although I have not shown the entire fran'ie in the drawings. In a preferred form the ,upper end ofthe rod 22 is free to move in an opening in the base 20, as sho-wn, so that when the rod is heated by the passage of current through the resistance material, the rod may expand vfreely and may contract when the current is cut oit. It is obvious that in this construction the resistance material may be connected in circuitin any suitable manner.

In -Fig. 8 I have illustrated a preferred form of connecting a plurality of resistance units. In this construction the insulating tubes are mounted upon two short rods, which like the rods shown in Fig. 8 do not extend entirely through the tubes. In the preferredl form these rods are formed in a substantially U-shape, as shown at 23, the arms of each U-shaped rod being arranged to fit within the ends of adjacent in sulating tubes. In a preferred form, the U-shaped members 23 are carried upon insulating bases 24, which' may form part of a frame, if desired. One or more of the rods 23 may be provided with loops 25 intermediate to their ends (Fig. 9),-so that they may be attached to a portion of the base 24 by meansof clamping bolts 26. Ina preferred form the ends of the adjacent units are brought up to these clamping bolts 26, as shownin Fig. 10, so that the circuit of the device extends in series successively through each unit as shown in that ligure. If desired, thelower rods 23 may be embedded in the lower base 24C,V and any number of units and supporting rods may be used.

In Fig. 10 I have illustrated a further preferred form of connecting the ends of adjacent units. As shown in` this construction several units may be made up from o-ne pieceof resistance material, and this resist-` ance material may be so formed that a connecting strip 27 of resistance material connects the units at the desired points, when they are mounted 'on their supports. Thus I am able to provide any desired number of units which are formed integral with each other, and thus avoid the loss', of time and expense incident to connectingthe several units together. It is obvious, however, that where it is advisable to use shorter strips of resistance material the ends of these strips may be connected to each other by any suitable means, as for instance by means of spot-welding, as indicated in dotted lines at 28 in Fig. 10.

If desired, instead of using an insulating tube formed of glass I may instead, for certain purposes, coat the metallic supporting rod with a covering of enamel or use a soft glass which becomes fixed to the rod, and in this manner produce a unit wherein the insulating sheath is integral with the support, the support being movable if desired. When enamel is used, this enamel may, if desired, have a higher melting point than the running temperature of the unit, so that the unit will not embed itself in the insulating material to such an extent as to cause a short circuit. For some uses, however, I nd it advisable for the resistance material to embed itself to a certain extent in the insulating support, since this gives a more stable support and a more unitary structure.v For some purposes I may, if desired, "coat therod with a coveringconsisting of two coats of enamel, the outer of which has a lower melting point than the inner, so that the temperature at which the resistance is embedded, while sufficiently high to soften the outer coat is not suiiciently high to soften the inner coat. Obviously, the resistance material may be embedded to any desired degree in the insulating material.

My improved electric resistance unit is of a-type well adapted to use either asa means for dissipating energy or asa means for generating heat for heating purposes. The

resistance material may be arranged upon the support in such a manner that the heat radiated is distributed evenly from the unit and is readily absorbed from the same by the atmosphere or the object to be heated. My improved unit may, therefore, be readily adapted to use as a heater for electric heating devices, wherein the devices are adaptedv to operate at ared heat. Further, byvvmy improved manner of mounting the resistance material upon the insulating support I am able to provide not only ameans for eifectually insulating the unit in such a manner that the resistance material engages .proved construction I am able to provide a unit which may be readily operated at high temperatures without any danger of breaking through-the insulation of the device or burning out the same. rfhis is particularly true in those constructions wherein a quartz tube is used. By the provision of my improved means of allowing tor the eX- pansion and contraction of the supporting 1od for the unit, l am able to efect-ually prevent any breakage of the unit or any distortion of its support, the insulating support being freely movable. when desired upon the rod and the rod itself, when desired, being freely movable in its frame. Where it is not desired to use the device for high temperatures7 instead of using the quartz tube may'employ a glass tube or the coatings ot enamel which have mentioned. By my improved manner oit' mounting the resistance unit or a plurality of these units in a trame, l am able to prevent not only the distortion of the devicei due to the contraction and expansion, but l am also able to use the supporting rods tor the device as the terminals for the same, and in this manner eut down the number of 'necessary parts.

Further, a plurality of these units may be formed of. a single strip of resistance mate rial, portions ot' the same being wound on the several units; or, it desired, a plurality of strips of resistance material may be used, the ends being electrically connected as by spot-welding.

While have in this application described severatforms which my invention may assume in practice, I do not wish to be limited to these forms chosen for purposes of illustration, but wish rather to cover within the scope of this application all of those forms oi' my invention falling within its spirit.

Vhat claim as new and desire te secure by Letters Patent is A resistance unit comprising a supportingrod and a convoluted resistance carried by said rod and having its convolutions surrounding the same, the convolutions of said. resistance being triangular in form and each convolution having all three sides thereoif engaging said rod tangentially so that side is firmly heldv against said rod by its two adjacent sides and each convolution is spaced from said rod except at its points tangential engagement therewith.

ln witness whereof, l have hereunt scribed my name in the presence et two nesses.

EDTWN N. LGHTFGGT,

Witnesses H. D. HADAWAY, Jr., Geenen J. MALLON.

CIJ 

